1) Field of the Disclosure
The disclosure relates to air vehicles. In particular, the disclosure relates to unmanned and manned air vehicles with detachable inflation systems and devices.
2) Description of Related Art
Unmanned air vehicles (UAVs) are uncrewed aircraft vehicles that are capable of controlled, sustained, powered level flight. Such UAVs may be used in commercial, civil, and military applications. UAVs may be categorized in terms of their altitude and endurance or flight duration. High altitude, long endurance (HALE) UAVs are those that can typically fly at an altitude of over 30,000 feet and for six hours or more. HALE UAV configurations typically benefit from large, high aspect ratio wings. An aerially deployed HALE UAV may use a launch vehicle, such as an intercontinental ballistic missile, to rapidly deploy anywhere on Earth. However, such a UAV must deploy from a comparatively small volume present in a launch vehicle such as a nose cone. This may make traditional aircraft wings infeasible. As such, aerially deployable UAVs may use inflatable wings that can be stored deflated and packed, greatly reducing the volume the UAV occupies. The wings may be constructed of a fabric, coated so as to prevent gas leaks, and filled with a high pressure gas. The wings typically require a large volume or mass of high pressure gas for initial inflation and sometimes a smaller volume or mass of high pressure gas to replenish or make up for lost differential pressure which may result from leaks, heating and cooling due to diurnal cycling or altitude change, or changes in ambient pressure. For example, the additional replenishment gas may be used for making up for leakage and can be referred to as “make up gas”. With typical aircraft, the aircraft starts from the ground and ascends, and the atmospheric pressure decreases. With aerially deployed UAVs, the UAV starts from a higher altitude and descends. In order to have a structurally rigid wing, a minimum differential pressure must be maintained across the skin of the wing. As the UAV descends, the atmospheric pressure increases, so that the change in pressure decreases. Thus, additional make up gas may need to be pumped into the inflatable wings or other inflatable structures to make up for this effect.
Known UAVs with inflatable wings or other inflatable structures may leave their inflation apparatus on the ground. However, this can prevent the use of the replenishment or make up gas which may be necessary for the flight or mission. In addition, this can limit the distance or range that the UAV can cover if the inflatable wings lose pressure during the flight.
Alternatively, known UAVs with inflatable wings or other inflatable structures may carry their inflation apparatus internally within the UAV. High pressure gas is typically stored in inflation storage devices such as tanks or solid gas generator containers similar to solid rocket motors. Such tanks and solid gas generator containers are useless once they are empty and are typically retained on the UAV for the duration of a flight or mission. Retaining the storage tanks and the solid gas generator containers for the duration of a flight or mission may act as a weight and volume penalty to the UAV. This may increase the drag of the UAV and may reduce key performance parameters such as endurance, altitude, and payload. In addition, the wings have to be larger in order to accommodate the added weight, and the entire UAV must then increase in size to accommodate the larger wings. Moreover, when pressurized tanks or bottles are opened, as the gas expands, it cools, and cold fluid is injected into the inflatable wings or other inflatable structures. This requires that the inflatable wings or other inflatable structures be constructed of a material designed to withstand cold temperatures. Additionally, the cold gas has a higher density than if it were at ambient temperature requiring more gas than would have been necessary and venting as the gas expands after absorbing heat.
In addition, there are known systems to inflate the wings or other inflatable structures of UAVs without the use of stored compressed fluid. One known system uses a chemical reaction of solid materials that provides a high temperature exhaust or propellant to inflate the wings. However, this requires that the inflatable wings or inflatable structures be made of a high temperature resistant fabric that can withstand the high temperature exhaust. Burning such propellant inside the inflatable wings or inflatable structures requires the fabric and coatings to be insulated or capable of withstanding very high temperatures and local pressure spikes. This limits the types of fabrics or coatings available or requires insulation. Such options are likely to increase the overall weight of the UAV. Moreover, once the inflatable wings or other inflatable structures are inflated, the propellant may cool rapidly, and the inflatable wings or other inflatable structures must be re-pressurized. This may require additional gas generator cartridges, another combusting product, or another pressurized gas source.
Accordingly, there is a need for an air vehicle with one or more inflatable structures having a detachable inflation system that provides advantages over known systems.